On most days when San Diego has reached the century mark, it has hit 100 and held for an hour or two. Then some semblance of a sea breeze has kicked in, because the much cooler air over the ocean is drawn inland by the heat over the land. That breeze generally knocks the temperature down into the 90s.

Fifty years ago, the sea breeze took the day off. It was 105 or above for six hours and 100 or higher for seven. At midnight, it was still 80 degrees.

The heat wave that included the record-setting day caused, among other things, the deaths of 200,000 chickens, loss of power at thousands of homes and many vehicles to stall because of “vapor lock.”

When again?

It’s been 25 years since San Diego’s official high temperature has topped 101. Yet scientists are concerned that coastal areas are becoming more susceptible to deadly heat waves because of climate change.

Alexander Gershunov, a climatologist at the Scripps Institution of Oceanography, said he has studied California heat waves in great detail, although he hasn’t looked at San Diego specifically.

In a study with Scripps colleague Kristen Guirguis, the scientists concluded that desert heat waves should become relatively less intense while coastal heat waves are projected to intensify. Gershunov said the trend in coastal zones is toward more humid events with hot nights. Those conditions make it feel more uncomfortable.

“Given the high coastal population density and low acclimatization to heat, especially humid heat, this trend bodes ill for coastal communities, jeopardizing public health and stressing energy resources,” the scientists wrote.

In the short term, San Diegans have no super hot spells — dry or humid — to worry about. Temperatures are not expected to top the low 80s for at least the next week.

U-T news librarian Merrie Monteagudo contributed to this report.

San Diego has hit 100 degrees or higher 26 times since 1878, but just twice in the past 24 years. Here are the last 10 times the city reached 100 degrees:

Sept. 15, 2012: 101 degrees

Nov. 4, 2010: 100

Sept. 25, 1989: 100

Sept. 4, 1988: 107

Oct. 3, 1987: 104

Sept. 8, 1984: 100

June 16, 1981: 100

Sept. 15, 1979: 100

June 10, 1979: 101

Sept. 25, 1978: 101

San Diego’s 10 hottest days

Sept. 26, 1963: 111 degrees

Sept. 17, 1913: 110

Sept. 4, 1988: 107

Oct. 14, 1961: 107

Sept. 21, 1939: 106

Oct. 3, 1987: 104

Oct. 22, 1965: 104

Sept. 27, 1963: 104

Sept. 1, 1955: 104

Sept. 23, 1975: 103

Note: San Diego’s official weather station has been at Lindbergh Field since 1940. From 1913 to 1940, it was on F Street, between Union and State.

Source: National Weather Service

waits out the brutal heat on Sept. 26, 1963, while sitting in the water of Mission Bay, hoping for a bite. U-T file photo